plaster-msg - 3/17/99 Use of plaster in period. References. How to use. NOTE: See also the files: casting-msg, frescoes-msg, painting-msg, tiles-art, pottery-msg, block-printing-msg, masks-msg. ************************************************************************ NOTICE - This file is a collection of various messages having a common theme that I have collected from my reading of the various computer networks. Some messages date back to 1989, some may be as recent as yesterday. This file is part of a collection of files called Stefan's Florilegium. These files are available on the Internet at: http://www.florilegium.org I have done a limited amount of editing. Messages having to do with separate topics were sometimes split into different files and sometimes extraneous information was removed. For instance, the message IDs were removed to save space and remove clutter. The comments made in these messages are not necessarily my viewpoints. I make no claims as to the accuracy of the information given by the individual authors. Please respect the time and efforts of those who have written these messages. The copyright status of these messages is unclear at this time. If information is published from these messages, please give credit to the originator(s). Thank you, Mark S. Harris AKA: THLord Stefan li Rous Stefan at florilegium.org ************************************************************************ From: ALBAN at delphi.COM Newsgroups: rec.org.sca Subject: Plaster of Paris Date: 13 Mar 1998 22:58:17 -0500 Constance De LaRose said >I learned that the most common ceramic form material used is >plaster of paris. Guess what, plaster of paris is out of period so >it was back to the research to learn that they used porous >earthenware molds. Not that I would ever suggest that someone not do research on better materials for mold making, but, um, er, Constance? Plaster of Paris _does_ seem to be period: General reference: The Encyclopaedia Britannica, 15th ed. (1981), vol. VIII, p. 30: "Used since ancient times, plaster of paris is so- called because gypsum was early used near Paris to make plaster and cement." Specific reference: Cennino Cennini (in his _Il_ _Libro_ _dell'Arte_, trans. by Daniel V. Thompson, jr., New York; Dover Publications, Inc., 1960. ISBN 486-20054-X; the original's a mid-fifteenth century Italian work) uses Plaster of Paris for the making of molds from life. "Have the man or the woman stretched out; and have him put these little tubes into the nostrils of his nose, and have him hold them himself, with his hand. Have some plaster of Paris ready, made and roasted, fresh and well sifted. Have some tepid water near you in a basin, and put some of this plaster briskly on top of this water. Work swiftly, for it sets fast; and do not get it either too liquid or not enough so. Take a glass: take some of this preparation, and put it on, and fill in around the face with it." Of course, whether it was used for Constance's purpose in period, I do not know - but at least the stuff itself is period. (And for those of you wanting to cast from life with PoP, don't. It gets hot to the touch, ver y hot; I once measured a batch with a thermometer, and it topped at 125 degrees Fahrenheit. There are other ways of life casting. . . ) Alban, whose database of shtuff amazes even him. . . Date: Tue, 2 Feb 1999 16:27:53 -0700 From: "J. A. Smith" To: Subject: Re: Plaster on Wood? From: Rikki Mitman >Has anyone made a plaster cast of a wooden object to use as a mold? Would >the plaster stick to the porous wood as badly as I suspect? > >Teleri ferch Pawl A friend of mine suggests using vaseline, much like you do when you make casts of people. Lady Renna of Battersea, Caer Mithin Halle, Outlands Date: Wed, 3 Feb 1999 02:24:47 -0600 From: Roberta R Comstock To: sca-arts at raven.cc.ukans.edu Subject: Re: Plaster on Wood? On Tue, 02 Feb 1999 17:13:53 -0600 Rikki Mitman writes: >Has anyone made a plaster cast of a wooden object to use as a mold? >Would the plaster stick to the porous wood as badly as I suspect? > >Teleri ferch Pawl I haven't tried it, but would probably want to put somethingon the wood to keep the plaster from sticking. Or maybe try making a clay impression of the wooden object and then a plaster cast from the clay? hertha Date: Wed, 03 Feb 1999 11:56:49 -0800 From: Lady Eleanor To: sca-arts at raven.cc.ukans.edu Subject: Re: Plaster on Wood? A lot of art supply stores and craft stores carry mold making materials. There is a material...which I can not remember the name of at the moment..., but I believe there are several brand names on the market, that is rubbery and flexible when set. It peels right of the positive that you are casting, and is specifically made for molds that have heavy undercuts, and such. If you wish, I will see if I can find the name for you. I think this might cause you a great deal less aggravation than starting right from plaster, which is brittle, heavy, and very well might stick to a number of places on your original even with careful application of vaseline or some other release material. After you have your rubber-ish mold, then you would cast your plaster copy in that. I hope this is of some help. Eleanor, Lady Leycestershyre Date: Wed, 03 Feb 1999 12:45:30 -0800 From: Lady Eleanor To: sca-arts at raven.cc.ukans.edu Subject: Re: Plaster on Wood? I can't find my art supplies catalogs at the moment...(arrrgggh!)...but, here is one product that I've heard works well...never used it myself. It's called Instamold...mixes with water and sets in 2 minutes. Here's a web page that carries it. I'll see if I can find more for you. http://www.activa-products.com/molding.htm Eleanor Date: Wed, 03 Feb 1999 13:13:05 -0800 From: Lady Eleanor To: sca-arts at raven.cc.ukans.edu Subject: Re: Plaster on Wood? Further source info... Check this site... http://www.texasart.com/ Go to the "Catalog" button (the yellow crayon, at the bottom of the screen). Then go to #16 Clays, Casting, Sculpture and, Molding Supplies. This will download a .PDF file for you (380K, I think). Some of the products you want to look at are, Pliatex Mold Rubber, Moulage (good for face casting), and Silicone RTV Mold Making Rubber. Also, you might want to look at this link for a huge variety of art supply houses. You might find other products or better prices at some others. I get Texas' catalogs frequently...but haven't placed an order yet, so don't know how their customer service may be. I'd check several sources before you decide. :-) http://www.handilinks.com/cat1/a/a150.htm Lady Eleanor Date: Wed, 3 Feb 1999 15:50:05 -0800 (PST) From: sion warwick To: sca-arts at raven.cc.ukans.edu Subject: Re: Plaster on Wood? Another consideration is RTV (room temperature vulcanizing) rubber. Its usually available at commercial plastic suppliers. I use GTE's RTV11, which may be difficult to get (gives off dangerous fumes and is supposed to only be available to contractors - just tell them you are a contractor and use a little bravado and they should sell it to you - works for me). There are also other versions available. You just need to make sure they are rated to ~700 degrees or so for pewter. It is a two part mixture like epoxy. Just make sure that it is in a well ventilated area while curing. It takes about 24 hours to harden and about 1 week to completely cure. I've found that when it is heated during the casting process it gives off some fumes, so I always have a fan going. Here's a quick way to make a mold of an object: build a frame using legos thats about twice the size of the object and put it on a board. Put a layer of clay in the bottom of the frame and sink the object halfway into the clay. Build a sprue with clay from one side of the object to the lego frame. Mix RTV and fill the lego frame, making sure the object is covered by at least 1/4 inch of rubber. Let cure 24 hours, then lift lego frame from board and remove clay, leaving only enough to form the sprue. Slather it all in vaseline (the RTV cures to itself really well!), then fill that side with RTV, again making sure the object is covered by 1/4 inch rubber. Let cure 24 hours, then remove from frame and let cure 1 week. When casting with the rubber mold, use something rigid (like masonite pieces) to sandwich the mold when you are holding it, or it tends to gap and leak hot metal. Also, I recommend pressing a small lego piece bumpy side down into the clay before pouring the first RTV half to create registration marks. Helps hold the mold together without it slipping. Any other questions, feel free to contact me Lady Sion Date: Thu, 04 Feb 1999 15:44:48 -0700 From: Curtis & Mary To: sca-arts at raven.cc.ukans.edu Subject: Re: Plaster of Paris may be period plaster was molded and carved and used to decorate and elaborate the frames for Altarpeices in the church. I believe also some secular works. Mairi, ATenveldt Date: Thu, 4 Feb 1999 22:11:15 -0500 From: "Helen Schultz" To: Subject: Re: Plaster of Paris may be period Slaked plaster (a purified form of plaster of paris) was used to make one of the gilding bases for Gold Leafing in manuscripts. Katarina Helene Date: Wed, 17 Feb 1999 03:04:26 EST From: To: sca-arts at raven.cc.ukans.edu Subject: Re: Plaster on Wood? On Tue, 02 Feb 1999 17:13:53 -0600 Rikki Mitman writes: >Has anyone made a plaster cast of a wooden object to use as a mold? >Would the plaster stick to the porous wood as badly as I suspect? > >Teleri ferch Pawl I'm running behind and someone may already have mentioned this, but in making plaster casts of items for use with clay slip, we use "green soap" - it's liquid soap and it stops the plaster from sticking to your original. You should be able to get it at a good ceramic/pottery supply store. As for someone's comment about being sure you can get the original out - build yourself a wooden frame as deep as your mold needs to be, coat the sides and bottom with green soap. Fill it half full and press your original object halfway into the plaster. You will have to support it until the plaster dries enough that it doesn't sink. After the plaster is totally hard, coat the surface with green soap and fill the frame the rest of the way with plaster. This gives you a mold that will easily split in half without destroying the mold. You didn't mention what you were going to use the mold for (or I missed it - I"m speed reading...). If it's to pour something liquid (like slip), you need to work a channel into the mold (I use a dowel, or make a clay plug that butts up against the original). If your original has pokey out parts, you have to plan carefully, otherwise you end up with a mold that won't open after you've poured your casting material into it. Ealasaid Edited by Mark S. Harris plaster-msg Page 5 of 5